Compounds generating an acid by light irradiation are useful for cationic polymerization with an acid as a catalyst, and image-forming materials utilizing, for example, coloration and discoloration of dyes with acids.
Compounds of this type heretofore known include Lewis acid-generating compounds typified by aryl diazonium salts described in S. I. Schlesinger, Photographic Science and Technology, Vol. 18, page 387 (1974), etc.; onium salts typified by diaryl iodonium salts described in J. V. Crivello et al., Macromolecules, Vol. 10, page 1307 (1977), etc.; oxime sulfonic acid esters described in European Patent 199672, etc.; N-hydroxyimidesulfonic acid esters described in U.S. Pat. No. 4,618,564, etc.; and Bronsted acid-generating compounds such as nitrobenzylsulfonic acid esters described in Macromolecules, Vol. 21, page 2001 (1988), etc.
However, many of these compounds are sensitive only to ultraviolet light, and their sensitivity to light of from the near ultraviolet region to the visible region (i.e., the wavelength region longer than the 300-350 nm region, more specifically, the wavelength region of from about 350 nm to about 600 nm), such as light of an argon laser, is low.
The 9,10-dialkoxyanthracenesulfonic acid 4-nitrobenzyl esters described in JP-A-64-18143 (the term "JP-A" as used herein and hereinafter means an "unexamined published Japanese patent application") are known to be sensitive to light of from the near ultraviolet region to the visible region. However, the compounds disclosed in JP-A-64-18143 have a low reactivity and compounds having a higher reactivity are not known in the art.